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Cucumber green mottle mosaic virus was very widespread in cucumber crops in the Lea Valley in 1964. Experiments on the effect of this virus on yield indicated that losses of approximately 15 per cent occurred with early infection. Later infection had little effect on yield. Dry heat treatment of infected cucumber seeds at 70°C for more than one day was sufficient to inactivate the virus and these results were also confirmed using virus-impregnated filter paper squares. Cucumber seeds were found to tolerate dry heat treatment at temperatures of 75°C and 80°C with little adverse effect but, at 80°C, germination was delayed and the cotyledon leaves were distorted. In a commercial trial, over 45,000 cucumber plants free from symptoms of the virus were raised from infected seeds which had previously been heat treated at 70°C for three days. [ABSTRACT FROM AUTHOR]

The present paper is the first part of number two (B) in a planned series of four, all dealing with the annual rhythm of production of gramineous plants. This paper reports a two years experiment in photothermostats. The experiment was carried out in thermostats with electric light. The heat from the lamps was reduced through mantles of circulating water. The temperature varied around a mean of 17°C. The electric light was on during 16 hours a day and the rest of the day it was dark. The humidity varied around 61 %. The content of CO2 in the air was continuously determined. The plants were sown every fourteen days in brick pots, standing on deep plates of glass. They were harvested along with the roots after four weeks of growth. The capacity of germination of the seed was tested before every seeding in the first three quarters of the experiment time (Table I). The different seedbeds and experimental plants are listed on page 142. Some series received nutrient solution, others not. The nutrient solution is described on page 145. It was given in water solution after the seedings, and fourteen days later on the plates. Watering with distilled water was given on the plates every third thy. The data are graphically represented in Figs. l-6, as described in the text. All growth curves are typically unimodal. They have summer and autumn minima and winter and spring maxima. These variations are the same in both experimental years. Only the amplitude increases on addition of nutrient solution. For the first category of curves by as much as 300 % of the lowest figures. All curves for roots, with and without nutrient solution, had about the same amplitude. The curves for tops, without nutrient solution, had about the same amplitude as the curves for roots in all experimental series (Figs. 1-6). As a consequence, the root weight in per cent of tops was very high in the series without nutrient solution - 112 % - (Table 3), and in all curves it was the highest during periods, which had a low production. The present paper is mainly presenting the data, and further discussion is postponed until the data for another two year experiment in thermostats are presented. In that other experiment, analyses are made both on the soil before each seeding and of the tops of the plants after each harvest. Literature will be given in a later paper. [ABSTRACT FROM AUTHOR]

The purpose of this paper is to use a recent development in statistical theory known as parametric modeling to forecast wheat yields in the United States, Canada, Australia, and Argentina. The essence of this approach is that the data are used for identifying and estimating random components in the form of moving average and autoregressive processes. It does not identify and measure structural relationships as is attempted when forecasting with econometric models. Exponential smoothing is also used to forecast yields in the United States and Canada. The Thiel coefficient is then computed to determine the forecasting accuracy of parametric modeling compared with exponential smoothing. [ABSTRACT FROM AUTHOR]

SUMMARY In investigations into the relationship between mean plant density and crop yield, an inverse power response curve has often been used. In this paper the theoretical properties of a family of these curves are examined, including situations where two or more such relationships are being compared. Methods of fitting these response models are given. When response curves are fitted to experimental data it is usually desirable to summarize the data as briefly as possible and this leads to a search for parameter invariance. A formal scheme for analysing data by looking for invariance of parameters of the response curves is proposed and methods are given for fitting the various constrained models that this involves. These methods are illustrated in two examples. [ABSTRACT FROM AUTHOR]

Examines the relationship between the growth and yield of herbage grasses in pure stands and their growth and yield when they are grown in mixtures. Relationship between pure stand and competitive performance of grasses; Possible explanations for differences between relative yields of different components of a mixture; Tendency of the mixtures to yield more than the mean of the yields of their two components.

Presents a comparison of yields from plots sown with a single species or a mixture of grass species rye grass, meadow fescue and a triploid hybrid, under grazing and hay management. Conditions under which yields from mixed plots may exceed those from pure plots; Possible explanation for greater yields from mixed plots; Reason for decrease in the intensity of competition by mixing the grass species in plots.

Deals with a study which developed a methodology for assessing the relative advantage of green revolution high yielding varieties in various regions in the U.S. Description of the green revolution experience; Contribution of green revolution high yielding varieties to aggregate production in Asia and North Africa; Role of green revolution in agricultural development.

The article examines the reproductive behavior of natural populations in varying environment by generating model that determines the condition when it is optimal for the whole population to reproduce, and when it is optimal for only a fraction of the population to attempt to reproduce. It examines the viability, reproduction and differential viability of reproducing organisms. The prediction of the generated model is that a reproduction fraction less than 100% is expected in plants which have a long reproductive period and a high viability during this period. It predicts a 100% reproductive fraction when the yield of progeny is high and dependable. It concludes that the optimal germination fraction either increases or decreases based on the level of expectation and variety of yield.

The article focuses on the analysis of growth of Molinia caerulea and Dactylis glomerata or peat. There were two climate environments were employed in an attempt to separate the relative effects of mineral nutrition and climate on these grasses. The object of these studies are to define the ways in which plant growth is limited on high-level blanket peat at Moor House National Nature Reserve where the temperatures are similar to those at sea level in Iceland. The result of Molinia at Moor House in the second year reveal both higher mean yield values for plants which received nitrogen in the first year and substantial result for Dactylis in the first year.

The article presents a discussion about the observations gathered about the existence of Theobroma Cacao in the island of Fernando Po. The article explores the effectivity of the fungicide control of cacao black-pod disease or the Phytophthora palmivora and analyzes other aspects of cacao yields, cultivation, and ecological climate. It compares cacao epiphytes observations in Nigeria to the general ecology of cacao cultivation in the said island. The article is also supplemented with information about geography, climate, parasitic and epiphytic plants, and the effect of rainfall to the cacao.

Shifting agriculture and the carrying capacity of the land are critically important in developing tropical areas. Signs of breakdown in shifting agricultural systems, such as decreasing crop yield and soil fertility, have long been recognized. Among the Tiv another indication of breakdown is manifest when proved cropping sequences are deliberately altered. The first dot map of Tiv population depicts high densities in the south-central part of the division, and the annual rate of increase of population among the Tiv is calculated at a little more than three percent. The areas of high population density display evidence of a degraded environment, and in these same areas a new crop rotational sequence has evolved. This altered cropping pattern, known as "bugh bu," appears to be the result of the carrying capacity of the land being exceeded; it is found in areas with population densities of about 400 per square mile (154.4 per square kilometer). [ABSTRACT FROM AUTHOR]

The article discusses the cereal yields on the Sussex estates of the Abbey of Battle during the later Middle ages in England. One of the general deficiency of most of the early studies of medieval productivity was the examination of yield data in almost complete detachment from the environmental, socio-economic and technical conditions, which seemingly influenced the production under review. The types of arable farming practised on the Battle Abbey estates in Sussex at Alciston, the principal estate and home-farm, Apuldram, Barnhorne and Lullington invest the yield data with special interest and importance. By the late thirteenth century, when the extant documentation first reveals the economy of the Battle Abbey manors, cultivation for commercial purposes flourished and this was most clearly manifested in the arable husbandry by the suppression of fallow on the best or most conveniently manured land. The density of seed sown per unit of land is a much neglected aspect of medieval farming despite the importance of the relationship between the seeding rate and the yield, which up to a certain point increases as seeding is intensified.

Investigates the possible absorption of simazine by the roots of potatoes leading to residues of unhydrolysed simazine in tubers in India. Effect of pre-emergence application of simazine on crop yield; Overview of an experimental method used to estimate the simazine content of potato tubers; Appearance of phytotoxicity symptoms in tubers from plants treated with different doses of simazine.

Copyright of Weed Research is the property of Wiley-Blackwell and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Weed Research is the property of Wiley-Blackwell and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Weed Research is the property of Wiley-Blackwell and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Weed Research is the property of Wiley-Blackwell and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Weed Research is the property of Wiley-Blackwell and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Weed Research is the property of Wiley-Blackwell and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Weed Research is the property of Wiley-Blackwell and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

This article investigates the relationship between crop yields and solar activity showing for cotton and apples, not only a clear relationship to solar and sky radiation but also a well-defined cycle in both these and other crops in the U.S. The article shows the yields of cotton, apples, and winter wheat since 1908. It is seen that a peak occurred in each simultaneously at intervals of six years throughout the 34-year period, with the exception of 1931 which culminated a five-year cycle, but again in all three crops similarly. Another striking feature of the yield behavior of these crops during this period is the sharp decrease in yield which occurred the year following the maximum yield of the cyclical period. Although the lowest yield of the cyclical period was not always reached then, it frequently was, and in no case was this year significantly higher than the minimum. Cotton shows the same cyclical tendency when yields are extended back to 1898, one six-year and one four-year cycle occurring in this 10-year period. With regard to other crops, maxima in the yield of peaches have occurred in the same years as cotton, apples, and winter wheat since 1926, and in the yield of peanuts since 1931.

This article talks about agriculture in Eastern Europe. As a result of overpopulation and underproduction, the agricultural output per head of the population of Eastern Europe is significantly low as compared with that in the U.S. According to the author, the small consumption of meat and other animal products in the region greatly affects the whole character of agriculture, as a consequent lack of fertilizing manure results in low crop yields. He explained that war affected Eastern Europe's agricultural production, with military operations precluding the cultivation of soil over considerable areas, peasants being driven away from their homes and their animals being carried away for military use.

The article discusses the theory of economic cycles and analyzes the correlation between crop yields and crop prices, the derived cycle of prices, generating cycles of products, cycles in the products of mines and cycles in raw materials. The major features of economic cycles are traceable to three primary laws, including the law of the generating cycle of raw materials, the law of demand for raw materials and the law of competitive price. Generating economic cycles are economic cycles which have their origin in non-economic causes and are themselves the originating source of derived economic cycles.

Focuses on the influence of crop yields on economy of the U.S. Ways in which general business conditions are likely to be affected by success or failure of the crops; Industries which are influenced by trends in crop yield; Influence of corn and cotton crops on the economy.

The section of "Long Vegetable Fibres" focuses on the production of traditional long fibres. Attempts have been made to make the products of traditional long fibres more competitive. These attempts were made on two distinct lines including, explorative work on minor fibres for substitution of the traditional fibres on geo-economic considerations, and the application of improved methods of cultivation and genetics for obtaining higher yields and qualities of traditional fibres. The possibility of using cotton-stem fibre as a substitute or diluent for jute has been explored. A number of cultural field trials have been conducted on sisal and Sunn hemp under the Indian Council of Agricultural Research to study the characteristics and yields of different varieties.

The article presents a study to estimate a long-term crude birth rate of the Chinese agricultural population. Two groups of data have been utilized in pursuing this objective. One group consists of data on crop-yield density in China according to divisions by province and the other on crude birth rates for areas. From the data, the following conclusions can be drawn: a negative relationship holds between crop-yield density and the birth rate in China and area differences in birth rates are real and not due to errors in the data. It should be noted that the negative relationship observed refers to the group aspect of the provinces in their general association of above median crop-yield density with below median birth rate, and vice versa. The reference to group aspect should also be borne in mind in the interpretation of the area differences in birth rates. Different estimates of the birth rate were obtained from the age data for the two sexes. However, when a uniform level of mortality is assumed, the average birth rates calculated for either sex on the basis of age data from certain groups of surveys are not far apart.

The results of a field, experiment with winter barley in which severe mildew occurred early in the autumn are described. Where the disease was controlled with ethirimol (‘Milstem’)* seed dressing, the production of adventitious roots and tillers in the autumn was significantly increased and more of the tillers developed to maturity leading to higher grain yields. [ABSTRACT FROM AUTHOR]

In nine experiments in 1966–68, fungicides applied on 8–12 occasions to plots of barley resulted in mean grain yield increases of about 40 per cent. Zineb increased yields by an average of 50 per cent in nine experiments and lime sulphur by 19 per cent in six experiments. In single experiments dichlofluanid increased yields but oxycarboxin did not. In 1968, fungicides applied on only two occasions failed to control disease and to increase grain yield. Large yield increases were associated with a good control of leaf diseases including leaf blotch (Rhynchosporium secalis), halo spot (Selenophoma donacis) and brown rust (Puccinia hordei). Mildew (Erysiphe graminis) was excluded by using resistant cultivars. The diseases were severe late in the season, usually at or after ear emergence. Yield increases were wholly due to an increase in grain weight (1000-grain weight). [ABSTRACT FROM AUTHOR]

Data obtained from experiments on the chemical control of wheat bulb fly larvae were used for regression analysis. In these experiments wheat (cv. Cappelle Desprez) was sown in November, or later, in eastern England in 1957-66. Up to 70 per cent of the variation in yield was accounted for by regressions of yield on measurements made in March of densities of plants and of larvae, and of plant development. The possibility of forecasting yields and of estimating yield losses is discussed. [ABSTRACT FROM AUTHOR]

This article examines the effect of irrigation on the yield of cauliflower and cabbage crops damaged by the cabbage root fly. A comparison of the responses of early summer cauliflower and summer cabbage crops grown under different soil moisture regimes was made between plants exposed to different levels of cabbage root fly infestations. Irrigation treatments gave the largest yield responses on plants kept free of damage throughout growth and on those damaged relatively later in growth. Plants not protected from early damage failed to respond sufficiently to irrigation to give an increase in yield equivalent to that of the combined insecticide and irrigation treatments.

This section focuses on the effect of Aphis fabae Scop. on the growth and yield of field beans in a garden plot. By June 29, 1948, the effects of the infestation were visible and showed a statistically significant reduction in mean total stem-length per plant or 22 percent as compared with controls; there was also a significant reduction of 11 percent in the mean number of stems per plant. The yield was greatly reduced on the infested plants, the mean weight of beans per plant being 58.7 grams for controls and 33.3 grams for infested plants. A significant correlation was obtained between mean individual stem-length per plant and degree of infestation using only infested plants, as well as between yield on total stem-length per plant and yield on number of stems per plant.

The objectives of this article are (1) to examine agricultural output in Burma, particularly rice, in relation to Burma's economic development needs and in relation to the present and prospective population of the country, and (2) to note the cultural obstacles to population control policies which arise because of the impact of Buddhist thought and philosophy. Though independent Burma has made a substantial degree of economic progress since 1948, per capita real income has still not attained the pre World War II level. Failure to achieve the prewar level of real per capita income is all the more disturbing in view of the considerable amount of foreign aid, both technical and financial, which has been provided. Current population estimates and estimates of future net annual population-growth rates seem to indicate that, despite atypical population characteristics in the past, Burma is fast becoming typical as regards population matters in the Far East. In view of the rate of development in the agricultural sector, particularly rice culture, and in view of Burma's dependence upon rice exports to provide finances for an economic development program, a rapidly growing population poses a serious threat.